London-wide air traffic control failure was caused by an unprecedented computer fault

Air traffic controllers workload was increased by the error, which was deemed unsafe

The computer error that caused the skies over London to be cleared of planes had never been seen by engineers before, according the company in charge of the system.

Air traffic control firm Nats said the computer error had restricted air traffic controllers’ ability to deal with high volumes of aircraft.

Nats said its systems were up and running against last night but that knock-on effects were still affecting airports today.

A company spokesperson explained that fault occurred when controllers tried to transition between two “states” of their system.

“Swanwick controller workstations provide a number of tools and services to the controller to enable them to safely control a high volume of air traffic,” the spokesperson said.

“In normal operations the number of workstations in use versus in standby fluctuates with the demands of the traffic being controlled.

“In this instance a transition between the two states caused a failure in the system which has not been seen before,”

“The failure meant that the controllers were unable to access all of the data regarding individual flight plans which significantly increases their workload.”

Heathrow Airport said 38 flights had been cancelled before 9.30am today and warned that there would still be logistical problems.

In a statement, a spokesperson said: “Following yesterday’s technical problem at the Nats air traffic control centre in Swanwick, operations have started up well at Heathrow on what is a very busy day.

“There will, though, be cancellations to some flights because aircraft and crew are out of position.

“Passengers due to depart today should check the status of their flight with their airline before travelling to Heathrow. We are very sorry for the disruption to passengers’ journeys.”

Gatwick Airport suffered from 16 cancellations and seven diversions of inbound flights yesterday. It reportedly is running smoothly today, however.

“We don’t expect to see any further significant disruption to our flights, for the remainder of the day,” a spokesperson for the airport confirmed.


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